The invention relates to the subject that is characterized in the claims, i.e., thiazole derivatives, process for their production and their use for the production of epothilone A, epothilone B or derivatives thereof.
It is known that the natural substances epothilone A (Rxe2x95x90H) and epothilone B (R=methyl) (compound I, DE 195 42 986 A1, DE 41 38 042 C2) 
have a fungicidal and cytotoxic action. According to references for an in vitro activity against breast and intestinal tumor cell lines, this compound class appears particularly advantageous for the formation of a pharmaceutical agent. Various working groups are therefore concerned with the synthesis of these macrocyclic compounds. The working groups start from different fragments of the macrocycle to synthesize the desired natural substances. Danishefsky et al. intends to synthesize from three fragments C(1)-C(2)+C(3)-C(9)+C(10)-C(20). The C(10)-C(20) fragment is a thiazole derivative, which could not be obtained free of diastereomers in a 15-stage synthesis (JOC, 1996, 61, 7998-7999). Freedom from diastereomers is often decisive, however, for the action and a requirement for the production of a pharmaceutical agent.
The object was therefore to prepare, in a manner free of diastereomers, suitable fragments, from which the macrocyclic compounds and derivatives thereof can be synthesized.
It was now found that the thiazole derivatives of formula II 
in which
R1 means C1-C4 alkyl,
R2 means any protective group that can be chelated,
R3 means hydrogen or C1-C4 alkyl,
Y means CO2R4, CHO, CHxe2x95x90CH2 or CH2R5,
xe2x80x83whereby
R4 stands for C1-C4 alkyl or an optionally substituted benzyl group,
R5 stands for halogen, hydroxy, p-toluenesulfonate or xe2x80x94OSO2B and
B stands for C1-C4 alkyl or C1-C4 perfluoroalkyl,
can be produced free of diastereomers, and are suitable for the production of epothilone A and epothilone B and derivatives thereof.
C1-C4 alkyl for R1, R3, R4 and B is defined as methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl.
Any protective group R2 that can be chelated is defined as, for example, benzyl radicals such as, e.g., benzyl, p-methoxybenzyl (PMB), silyl radicals such as, e.g., trimethyl-silyl, 2-(trimethylsilyl)ethoxymethyl (SEM), tetrahydropyranyl, methoxymethyl, benzyloxymethoxymethyl, benzoyl, acetyl.
Substituted benzyl group R4 can be, e.g., p-methoxybenzyl, 2,4-dimethoxybenzyl or a benzyl radical that is substituted by another electron-pushing substituent.
Halogen is defined as fluorine, chlorine, bromine and iodine, whereby bromine and iodine are preferred.
C1-C4 Perfluoroalkyl is defined as straight-chain or branched, completely fluorinated alkyl radicals, such as, for example, CF3, C2F5, C3F7, C4F9.
Compounds II can be produced according to the process that is shown in diagram I, in which the synthesis is depicted by way of example for compound IIa with R2=p-methoxybenzyl, R3=methyl and Y=CO2Et.
Starting from the naturally occurring (S)-malic acid (III), the xcex1-hydroxy acid function with trifluoroacetic acid anhydride/methanol (a) is converted into the mono-methylester. The acidic function that still remains is then reduced to alcohol with diborane in tetrahydrofuran (b). The (S)-(xe2x88x92)-methyl-2,4-dihydroxyester that is thus obtained is converted into the cyclic acetal (IV) with p-methoxybenzyldimethylacetal with camphersulfonic acid in toluene under reflux (c). The methylketone (V) is obtained from the methylester by reaction with one equivalent of methyllithium in 2 hours at xe2x88x92100xc2x0 C. (d). Reaction with a C2-, C3- or C4-organometallic compound, e.g., of a Grignard compound under common reaction conditions, results in the other radicals R1. In the Wittig reaction (c), the 2-methyl-4-thiazolylmethyltriphenylphosphonium bromide, which is accessible in two stages from 1,3-dichloropropanone, is combined first with sodium hexamethyldisilazide at xe2x88x9278xc2x0 C. in tetrahydrofuran before the ketone is added to it. After 1 hour and after heating to xe2x88x9240xc2x0 C., the reaction results in an E/Z-mixture (E/Z=3.6:1). The E-isomer (VI) can be separated by simple flash chromatography. Regioselective release of the terminal hydroxy group by reductive opening of the acetal with 4 equivalents of diisobutylaluminum hydride in methylene chloride in 4 hours at xe2x88x9220xc2x0 C. (f) produces a readily separable mixture (5.6:1 for the desired regioisomer) of the alcohol. After separation, the alcohol is converted into the corresponding aldehyde by Swern oxidation in one hour while being heated from xe2x88x9278xc2x0 C. to 0xc2x0 C. (g), and the aldehyde is reacted immediately to Wadsworth-Horner-Emmons condensation under Still""s conditions (h) with ethyl-2-diethoxyphosphinylopropionate or the Horner reagent that is suitable corresponding to the desired radical R3 with the addition of potassium hexamethyldisilazide, 18-crown-6 at xe2x88x9278xc2x0 C. for one hour in tetrahydrofuran. An E/Z-mixture (E/Z=6.2:1) of the xcex1,xcex2-unsaturated ester is obtained, from which the Z-isomer (IIA) can be separated in a good yield. The use of the trifluoroethylphosphonate derivative results in a better selectivity of 15:1. 
The compound of general formula IIa represents a central component of the synthesis of epothilone derivatives and epothilone itself.
The ester function in 11-position can be converted into any functionality that is required for the subsequent ring closure.
Derivatizations in 12- and 13-position (epothilone numbering system) are possible from the double bond. Thus, for example, conversion by Sharpless oxidation into the epoxide that is itself present in the epothilone:
In this respect, ester IIa is reduced with 3 equivalents of diisobutylaluminum hydride in tetrahydrofuran at xe2x88x9220xc2x0 C. (i) into a xcex1,xcex2-unsaturated alcohol, and then the double bond of the allyl alcohol is epoxidated in a diastereo-selective manner with 4 xc3x85 molecular sieve, titanium tetraisopropylate, D-(xe2x88x92)-diisopropyltartrate, tert-butylhydroperoxide in methylene chloride for 3 hours at xe2x88x9230xc2x0 C. (k). 
The hydroxy group in 15-position that is still present in protected form also allows derivatizations at this point or can be cleaved under conditions that are known in the literature.
Compounds with Yxe2x80x94CHO can be obtained by Dibal reduction of compound IIa in a way that is known in the literature.
Subsequent Wittig reaction results in compounds with Y=CHxe2x95x90CH2.
The compounds with Y=CH2R5 with R5=p-toluenesulfonate, (C1-C4)alkylsulfonate or (C1-C4)perfluoroalkylsulfonate can be obtained from alcohol (VII).
The compounds with Y=CH2-halogen can be obtained from, e.g., the compound with Y=CH2-p-toluenesulfonate or Y=OH in the usual way.
In contrast to the process of Danishefsky et al., only 10 stages are required for the synthesis up to the stage of the epoxide, and the thiazole derivative of formula IIa can be obtained free of diastereomers just like the epoxide. Another advantage consists in that the natural starting material that is used and the reactions of the synthesis allow larger amounts to be produced.
The further processing of the compounds according to the invention to epothilone A and B can be carried out as indicated in the reaction sequence below. The compound of general formula XI is further processed into epothilone B analogously to known processes by cleavage of the primary protective group, oxidation in 1-position, selective release of the 15-hydroxy group, as they are described by, for example, K. C. Nicolaou et al. In Nature, Vol.38-, 1997, pp. 268-272 and J. Am. Chem. Soc. 1997, 119, pp. 7960-7973: 
f) (i) iodide formation; (ii) sulfone coupling, 76.5%; g) desulfonation, 70%; h) desilylation, 98%; i) aldol reaction.
The examples below are used for a more detailed explanation of the subject of the invention, without intending that it be limited to these examples.
All reactions of organometallic reagents and all reactions in absolute solutions are performed in an environment that is devoid of air and moisture. Before the beginning of the test, the glass equipment that is used is heated several times in an oil pump vacuum and aerated with dry argon of the Linde Company. Unless otherwise indicated, all reaction batches are stirred magnetically.
Methylene chloride is dried on a basic aluminum oxide column of activity stage 1 (Woelm). After predrying on a basic aluminum oxide column over an 8:1 sodium/potassium alloy, diethyl ether is refluxed until the stable blue coloring of the benzophenone indicator is achieved and is freshly distilled off before use. Tetrahydrofuran (THF) is predried on KOH, filtered with a column that is coated with basic aluminum oxide and then distilled on potassium with triphenyl-methane as an indicator.
After predrying on calcium chloride, ethyl acetate (EE) is distilled off just like hexane (hex) before use for column chromatography in a rotary evaporator.
All reactions are monitored by thin-layer chromatography (TLC) on silica gel-60-aluminum foils with the UV-indicator F254 of the Merck Company. In most cases, solvent mixtures of hexane (hex) and ethyl acetate (EE) are used as mobile solvents. For visualization of non-UV-active substances, anisaldehyde glacial acetic acid/sulfuric acid (1:100:1) has been taken as a standard immersion reagent in most cases.
The preoperative column chromatography is performed on silica gel-60 of the Merck Company (0.04-0.063 mm, 230-400 mesh), whereby solvent mixtures of hexane (hex) and ethyl acetate (EE) or diisopropyl ether are used as eluant.
On an analytical scale as well as on a preoperative scale, the high-pressure liquid-chromatographic separations (HPLC) are performed on the module systems of the Knauer Company (pump 64, UV and RI detectors, columns and recorders), Waters/Millipore Company (Injection system U6K9) and Milton-Roy Company (integrator CI-10). For the analytical HPLC, in most cases a Knauer column (4,250 mm) with 5 xcexcm Nucleosil is used, and for preoperative HPLC, a column (16,250 mm, 32,250 mm or 64,300 mm) with 7 xcexcm or 5 xcexcm of Nucleosil 50 is used.
Color reagent I (F I): In the case of most compounds that can be reduced, 1 g of cerium(IV) sulfate in 10 ml of concentrated sulfuric acid and 90 ml of water produce an intensive blue color reaction during drying.
Color reagent II (F II): A 10% ethanolic solution of molybdatophosphoric acid represents another immersion reagent for detecting unsaturated and reducible compounds. In contrast to color reagent I, the molybdate-color reagent, especially pertaining to several functionalities, shows a broader color spectrum in virtually identical reliability.
Color reagent III (F III): 1 ml of anisaldehyde in 100 ml of ethanol and 2 ml of concentrated sulfuric acid represent an extremely sensitive color reagent that also likely shows the broadest color spectrum.
Color reagent IV (F IV): The vanillin immersion bath reagent is sensitive much like the anisaldehyde color reagent and like the latter shows an almost broad color spectrum.
Color reagent V (F V): 1 g of 2,4-dinitrophenylhydrazine in 25 ml of ethanol, 8 ml of water and 5 ml of concentrated sulfuric acid represent an excellent immersion reagent that responds selectively to aldehydes even without being heated and that responds somewhat more slowly to ketones.
Color reagent VI (F VI): A 0.5% aqueous solution of potassium permanganate indicates groups that can be oxidized by decolorization, whereby unsaturated, non-aromatic structural units react spontaneously without heating.
The 1H-NMR spectra are recorded with an AC 250, AM 270 or AMX 500 spectrometer of the Bruker Company with the substances as a solution in deuterated solvents and tetramethylsilane as an internal standard. The evaluation of the spectra is carried out according to rules of the first order. If a signal multiplicity that occurs cannot be explained in this way, the indication of the observed line assembly is done. To determine the stereochemistry, the NOE spectroscopy (Nuclear Overhauser Effect) is used.
To characterize the signals, the following abbreviations are used: s (singlet), d (doublet), dd (double doublet), ddd (6-line system with two identical coupling constants or an 8-line system with three different coupling constants), t (triplet), q (quartet), quint (quintet), sext (sextet), sept (septet), m (multiplet), mc (centered multiplet), br (broad) and v (masked signal).
The 13C-NMR spectra are measured with an AC 250 of the Bruker Company with CDCl3-signals at 77.0 ppm as an internal standard, whereby the portion resonances are broadband-decoupled.
abs.: absolute, Ar: aryl/aromatic compound, ber.: calculated, Brine: cold saturated common salt solution, c: concentration, COSY: correlated spectroscopy, DC: thin-layer chromatography, DDQ: dichloro-dicyano-quinone, d.e.: excess diastereomerism, DIBAL: diisobutyl-aluminum hydride, DMF: N,Nxe2x80x2-dimethylformamide, DMS: dimethyl sulfide, DMSO: dimethyl sulfoxide, ds: diastereoselection, EA: elementary analysis, e.e.: enantiomeric excess, EE: ethyl acetate, EI: electron impact ionization, eq: equivalent(s), eV: electron volt, FG: functional group, gef.: found, ges.: saturated, h: hour(s), hex: n-hexane, HMDS: hexamethyldisilazide, HPLC: high-pressure liquid chromatography, Hxc3xcnig Base: N-ethyl-diisopropylamine, HRMS: high-resolution mass spectrometry, HV: high vacuum, iPrOH: 2-propanol, IR: infrared spectrometry/infrared spectrum, J: coupling constant, LDA: lithium diisopropylamine, Lsg.: solution, Lsm.: solvent, Me: methyl, MeLi: methyllithium, min: minute(s), MS: mass spectrometry/mass spectra, NMR: nuclear-magnetic resonance, NOE: Nuclear Overhauser Effect, PCC: pyridinium chlorochromate, PG: protective group, Ph: phenyl, ppm: parts per million, Rkt.: reaction, rt: retention time, RT: room temperature (20-30xc2x0 C.), Std.: hour(s), TBAF: tetra-n-butylammonium fluoride, TBDPS: tert-butyldiphenyl-silyl-, TBS: tert-butyldimethylsilyl-, tert./t: tertiary, TFA: trifluoroethanoic acid, TFAA: trifluoroethanoic acid anhydride, TFMS: trifluoromethanesulfonic acid, THF: tetrahydrofuran, TMS: trimethylsilyl, u: g molxe2x88x921.